Flotation process



United States FLOTATION PROCESS Charles H. G. Bushell, Montrose, British Columbia, and Harry E. Jackson, Rossland, British Columbia, Canada, assignors, by mesne assignments, to Nova Beaueage Mines Limited, Montreal, Quebec, Canada, a company of Canada No Drawing. Filed Dec. 16, 1959, Ser. No. 859,845

11 Claims. (Cl. 209-166) This invention relates to the recovery of niobium minerals. It is particularly directed to the separation, by froth flotation, of niobium minerals such as pyrochlore and niocalite from valueless or gangue materials in association with which such minerals are found in nature.

Pyrochlore and niocalite minerals are found in nature in relatively small amounts in ores which contain substantially larger amounts of minerals such as pyroxenes, feldspars, biotite, calcite, apatite and the like. There is an important problem in the recovery of these minerals from such ores in that it is diflicult to separate these minerals from waste or gangue material and thus prepare a concentrate of satisfactory grade with minimum loss of niobium values in the gangue material or tailings.

Conventional flotation processes involving the addition of known frothing and collecting reagents to an aqueous suspension or pulp of an ore, can be applied to ores which contain pyrochlore and/or niocalite and a float product can be obtained. However, the degree of separation of the niobium bearing minerals from waste or gangue material is not satisfactory. A large percentage of the niobium values contained in the ore is lost in the gangue material or tailings and the niobium conten of the concentrate is low.

Processes are known for improving the concentration, by froth flotation, of niobium-containing ores. For example, in one known process, a concentrate of niobium minerals is produced by providing a relatively small amdunt of 8-quinolino1 in addition to conventional flotation reagents in an aqueous suspension of niobium ore subjected to flotation. In another known process, an aliphatic diamine and an aliphatic monoamine are used with other flotation reagents to float pyrochlore in successive sta es.

five have found that the addition, with the conventional frothing and collecting agents, of a small amount of the compound known as catechol, or pyrocatechol, to an aqueous suspension of an ore which contains pyrochlore and/or niocalite, and which is subjected to froth flotation treatment, greatly improves the efliciency of the separation of niobium minerals from waste or gangue materials over that which can be obtained with known flotation processes including those cited above, with resultant improvement in the grade of the concentrate and an important reduction in the loss of desired niobium minerals in the gangue material or tailings.

Catechol, refered to as' such throughout this application, is known also as pyrocatechol; ortho-dihydroxybenzene; 1,2-benzenediol; pyrocatechinic acid;and.oxy-

2,975,895 Patented Mar. 21, l 961 phenic acid. It has the formula C H (OH) It is in crystalline form at atmospheric temperatures and is soluble in water.

Niobium minerals such as pyrochlore and niocalite are naturally occurring, relatively complex minerals. Pyrochlore is believed to contain niobium as the niobate of calcium and of other metals such as the alkali metals and the rare earth metals and may also include titanates and fluorides. Niocalite is a calcium niobium silicate containing fluorine and is found in some Canadian ores. Although niobium is believed to be present in the minerals as the niobate or silicate, the niobium content of the ore is usually expressed in terms of niobium oxide, for example, in terms of percent Nb O The catechol can be added to the aqueous suspension of ore particles, or ore pulp, as a solid, as it is readily soluble in water. However, it is preferred to add it to the pulp as an aqueous solution. The catechol appears to be oxidized or otherwise altered during agitation and aeration of the mixture of solids and liquid in the flotation operation. If desired, the catechol solution can be agitated and aerated before being added to the ore pulp, but usually it is more convenient to add the catechol solution as such. A 10% water solution of catechol is satisfactory, although stronger or weaker solutions can be used if desired. The catechol need not be added in refined form as commercial grades are found to be satis factory.

The concentration process can be operated with one major flotation stage or with two or more major flotation stages. if only one major flotation stage is used, the ore pulp can be subjected to agitation and aeration in a conventional flotation machine in the presence of a collector and a frother with added catechol. The pyrochlore and/or niocalite is concentrated in the float product. With an ore containing pyrochlore in amount equivalent to about 0.7% Nb O the grade of the concentrate produced by this one-stage method is about 2% Nb O In the preferred procedure, two major flotation stages are used. in the first stage, which is' conducted with conventional reagents and without the addition of catechol, constituents such as sulphides, biotite and some calcite are removed in the float, the pyrochlore and/ or niocalite remaining in the residue. in the second flotation stage, catechol and, if necessary, additional collector and/or trother, is added to the residual suspension of solids from the first stage to float the pyrochlore and/ or niocalite as a flotation concentrate. "this second flotation stage can, if desired, incorporate secondary flotation steps for cleaning and re-cleaning to produce a final concentrate.

in the first flotation stage of the two-stage method, the best results have been obtained at a high pH for example, from pH 10 to pH 13, using a conventional amine ,collector and a trother. The high pH is obtained by adding an alkali, such as caustic soda, to the ore pulp. Suitable collectors are reagents based on amines and diamines,

- meen 0, in which the alkyl group is derived from oleic acid, and Duomac T, in which the alkyl group is deare trade marks aplied to compounds sold by Armour Industrial Chemicals Company. Suitable frothers are commercial products such as pine oil, methyl isobutyl carbinol and a mixture of propylene glycol methyl others.

The second flotation stage in the preferred procedure is carried out with the addition of catechol at a relatively low pH, within the range of from about pH 2 to pH 10, and preferably from about pH to pH 7. The pH of the first stage residual pulp can be reduced by the addition of an acid or a suitable salt, such as sulphuric acid, hydrochloric acid, nitric acid, hydrofluosilicic acid or magnesium fluosilicate. Hydrofluosilicic acid and magnesium fluosilicate are the preferred reagents for reducing the pH as the concentration results are usually better with these compounds than with sulphuric, nitric and hydrochloric acids. After the pH value has been lowcred, catechol is added to the mixture of solids and solution. Additional amounts of collector and frother can be used in this second stage if desired ornecessary. The aqueous suspension of solids is then agitated and aerated to produce a pyrochlore and/or niocalite float product. The residue or gangue material can be retreated or discarded. The float contains the pyrochlore and/or niocalite and can be cleaned in one or more cleaning steps, if desired. Additonal catechol and other reagents can be used the cleaning steps. I

The amount of catechol used in the process is prefen ably within the range of /2 to 5 pounds per ton of ore. This range is not critical as larger amountsthan 5 pounds per ton and smaller amounts than /2 pound per ton, for example, 4 pound per tone, can be used by would not normally be economic. With amounts less than about /2 pound per ton, the loss of niobium in the tailings becomes excessive, and with amounts greater than about 5 pounds per ton, the cost of catechol becomes unnecessarily high having regard to the value of the increased amount of niobium values recovered from the waste or gangue material. About 2 pounds per ton of ore gives very satisfactory results.

In practice, the flotation concentration step may be preceded by conventional gravity separation operations, such as sink-float and tabling, or by desliming, sulphide flotation or other conventional ore dressing treatments to-prepare a uniform feed. Also, in practice the pH of the pulp normally is in the range of from about pH 5 to pH 7 for the catechol flotation step in both the single stage and the two-stage flotation operation. Although the examples illustrate that catechol iscifective in this process over a wide pH range of from about pH 2 to 10, extremes of acidity and alkalinity are undesirable in view of possible corrosion problems, excessive consumption of reagents and less effective concentration of niobium mineral. Also, the amount of fresh catechol added to the pulp in commercial operations will depend to some extent on the residual effective material in circulating solutions and on the nature of the ore being treated. Furthermore, the catechol' can be added in whole or in part to the cleaning steps of the single-stage and of the twostage operations. In such cases, catechol, or its effective derivative in the pulp, is cycled to the initial niobium mineral concentrating step, or rougher step, in recirculating solution. Various modifications of the process will be apparent to those skilled in the art, given the essenltial feature of our invention-the use of catechol as a flotation reagent for pyrochlore, and niocalite.

The process is operable with water as it occurs in nature but in some areas where the local water contains organic material, it may be necessary to subject the water for theprocess to a conventional aluminum sulphate treatment or other suitable water treatment to ensure satisfactory results.

The process has the advantages that niobium'can be recovered as a relatively high grade pyrochlore and/or niocalite concentrate with relatively low losses of niobium values in the gangue material or tailings from complex, low grade ores which normally are not amenable to treatment by concentrating processes of the prior art. It uses readily available reagents and conventional flotation equipment, and it is applicable to the usual cycling circuits of flotation operations.

In each of the following examples, 500 grams of niobium ore were use which contained the niobium equivalent of about 0.7% Nb O by weight. Examples 16 and 17 relate i110 a niocalite ore; the remaining examples are based on tests with pyrochlor ore. The ore was ground to about 90% minus 200 mesh, based on Tyler screens, i.e. about 90% by weight was made up of particles smaller than 74 microns. The degree of grinding required depends, of course, on the ore. With the pyrocnlore ore used in these examples, the pyro-chlore mineral was intimately associated with gangue minerals so that complete liberation of the pyrochlore could not be eflfected, thereby adversely affecting concentration results.

Each sample was dispersed in water to form a dispersion or pulp, having a volume of 2400 ml. Caustic soda was added to the dispersion to increase the pH to about 10, and the dispersion treated in Fagergren type laboratory flotation machines. In Examples 1 and 2, the first stage float product was collected as a series of products at diflerent time intervals with staged additions of the collecting agent, as indicated. In the remaining examples, similar staged additions were employed but the first-stage float was collected and assayed as one product, the flotation operation continuing until no further float was formed, that is, for about 30 to 50 minutes. Throughout the tests, the volume of pulp was maintained at about 2400 ml. by the addition of water as required. After the first-stage flotation step, the pH of the slurry retained in the flotation cell was reduced as shown in the examples and catechol was added to the slurry. The resultant slurry was conditioned by agitation for about 5 minutes before the second flotation stage was initiated. I g

The examples, exceptExamples 14 and 21, show the percentage of the weight of the original 500 gram sample, the percentage concentration of Nb O and the percentage distribution of the Nb O content of the original sample, in the first-stage float product, the second-stage float product, which is the desired niobium mineral concentrate, and the second stage waste material or tailings. Example 14 shows the results obtained when the secondstage flotation operation included a cleaning flotation step and the percentage by weight figures in this case apply to the first-stage float product, the rougher railings, the cleaning step float product and the cleaning step tailings. Example 21 shows the results obtained with on flotation step after the ore has been deslimed.

Examples 8 to 13 inclusive show the eflect of vary-v g other known process but generally, in the following examples, the first-stage float product contains calcite, biotite, apatite and sulphides. The second stage float product constitutes the pyrochlore and/or mocalit'e concentrate and the second-stage tailings product contains silicates such as feldspars and pyroxenes and also some cal cite. The major constituents of the pyrochlore ore used in these tests were, by weight, 25 to 40% pyroxenes, l5

to 40% feldspars, 15 to25% biotite, 7 to 25% calcite,

2 to 7% apatite, 'and 2 to 5% sulphides, with minor amounts ofmagnetite, 1% ilrnenite, and 0.5 to 1% pyro- 75.

chlore.

EXAMPLE 1 "Duomac T" 1 "M" Time 5 Percent Percent Added, g. Added Other Additives min. pH Product N510. Distribution 0.25 3 drops (0.056 NaOH 16 12. 50

0. 32 7. 4 n 16 12. 58 0.25 14 12. 40 0 1n 4 12. 22 0. 36 11. 2 n 10 6 12. 20 n 10 H s 5 12.0 0.34 3.3 0.; g. catechol.-- 6 7o 7 Taiiing---. 0133 1113 1 Duomac T" is N-alkyl trimethylene diamine diacetate in which the alkyl group is derived from tallow.

1 "MIC is methyl isobutyl carbinol which was added as the commercial product.

Duomeen 0 is an N-alkyl trimeth It was added as the commercial product.

EXAMPLE 2 "Duomeen 0" 1 "Dowfroth Time, Percent Percent Added, ml. 250" 9 Added Other Additives min. pH Product bzOs glariu on 0 2i 5 ml NaOH 12 12.28 0.25 12 12. 42 Float 0. 8. 6 0 2i 7 12. 5 0 10 6 12.25 0 1n 4 12.80 Float 0.37 10. 8 0 10 H so 4 12.08

a A 0.5 g. catechol.-- 6 36 g t 0a 5 drops. 5 drone s 8.35 19 L 5 ylene diamine in which the alkyl group is derived from oleic acid.

I Dowfroth 250 is a mixture of propyleneglycol methyl ethers. It is added as a 1% solution 01 the commercial product.

EXAMPLE 3 "Duomac T Percent Percent Percent Added, g. "MIO Added Other Additives pH Product Wt. Nb20 bDiflzrl- U. on

0.5 4 dr)ops (0.074 2g. NaOH 12.2 Float".-.

E. 2.5 g. MgSiFa. 5 0 {Float I 3.91 71.8 0.5 g. catech01-.--.-- Tailing.-.- 0.15 10.1

EXAMPLE 4 0.5 3 drone g N 2)? F 12.3 2. 12.3 g. g 1 o 0a 2.4 0.5 g. catechol {Tailing 51.5 0.23 15.3

EXAMPLE 5 0 5 a drone 2 g. NaOH 12.0 F1oat.- 0.3 17. 0 3 gb 53 Float"-.- 3.4 04.9 05 g. catecm Tailing...- 0. 3 17. 0

EXAMPLE 0 0 3010 15- 2 1 73011 11. 0 goat... 2 12. 0 1. 3.2

0a 0.5 g. catechol {Tailing-..- 70.3 1.13 84.0

EXAMPLE 7 I 0.45- 3 drrm 2 gd Naorr 12.0 11052---" 33.; g g 2 1................ O3. 1.8 0.01 1 drop 0.5 g. catechol {T0iliflg 50.5 0.64 40.0

EXAMPLE 3 0.45- 3 dron 3 Nggg 12.1 24.5 0.20 7.7 g. g 5-- dd 9.0 1.75 42.0 (No cateehblL. {Taiiing...- 55.0 0. 50.3

EXAMPLE 0 2g. NaOH 20.2 0.32 0.5 2.5 g.Mgs1F.-- 10.1 5.03. 54.2 0.125 g. catechoL- 60.7 0. 66 36.0

EXAMPLE 10 Duomac T I l V 2 Percent Percent 1 515505 Added, g. MIO"Added Other Additives pH Product Wt. NbnOs Distribution 0.45 3 drops 2 2.515011 11.0 Float"-.- 32.5 0. 32 11.5 2.5 g. MgSiF 5 1 {Float. 9.5 5.15 54.2 0.5 g. catechol Teilingm. 57. 9 0. 53 34. 4

EXAMPLE 11 Float 14. 0. 18 2. 9 Float 7. 6 5. 95 51. 9 Tailing 78. 4 0. 49 45. 2

EXAMPLE 13 0.45 3drops 2g.NaOH 12.0 Float 18.3 0.26 5.5 2.5 4 Float.-- 14.5 4.68 79.1 1.25 g. catechol Toiling... 67. 2 0. 20 15. 4

EXAMPLE 14 This example shows the results obtained when the second-Stage float product is treated in a cleaning flotation step with additional catechol V 0.5.... 3 drops N121 11. 8 Ioot]. 45.5 0. 33 19. 5

g. g 1 oug or 0.5 g.-catechol. 4 Tailing. 5 18 5 0.5 g. catechol. Float 1. 9 23. 3 56.8 Cleaner 7. 1 1. 44 13.1

Taiiing.

EXAMPLE 15 In this example, the feed to the first flotetion step contained niobium in amount equivalent to 1.12% Nbgog. This feed was produced by subjecting the ore (about 0.7% Nbzoa) to a preliminary sink-float operation. The test was made with 500 grams or sink product.

0.5.. 3drops In the following Examples 16 and 17 the, ore treated contained niobium in the form of nio calite. In this. ore, the minerals were not so finely disseminated as inthe pyrochlore ore. The greater degree of liberation probably accounts for the lower niobium content of the tailings. Pure nioealite contains only 15 to 20% Nb20 compared with to N b305 in the pyrochlore of the other examples. The nioealite ore contained about 0.7% Nba0 EXAMPLE 10 0.3 3drops 12.0 52.2 0.118 34.5 5 2 8.6 5. 05.5

' 39.2 Trace EXAMPLE 17 0.3 Sdrops 2g.NaOH 44.2 0.30 17.85 0.05 3g. MgSiFa..- 0.7 0.07 79.00 1.0 g:0otech01 46. 0 0. 05 3. 09

EXAMPLE 1s 4 11. 9 Float 10. 4 0. 20 ,3. 7 msm 1 9 {Float 6.8 2.70 23.5 0.5 g. catechoi. Tailing 76. 7 0. 84 72. 5

EXAMPLE 19 3 at 3 3mm g 5 12. 0 27.2 V 0.27 s. 5 tops g. g l V 1 w e; 5-5 0.5g.cateehoi. r

EXAMPLE 20 "Duomac T" Percent Percent Percent Added, g. MIOAdded Other Additives pH Product Wt. Nb20 Igisitiriu on 0.45 3 drops 2 g. NaOH 11. 9 Float 29. 2 0.26 9.4 1 g. MgSiFa 9 9 {Float 9. l 2.05 23.0 0.5 g. catechol Tailing. 61. 7 0. 89 67.6

In the following example of a single stage flotation operation the ore was subjected to a preliminary desliming treatment and the resultant residue was subjected to flotation after the addition of catechol.

A 500 gram sample of pyrochlore ore, as used in previous examples,

was deslimcd by agitation with water followed by decantation of turbid liquid. The settled solids were then dispersed in water to produce a slurry of 2400 m1. volume.

The flotation step was carried out in the usual manner.

EXAMPLE 21 2 M as as a: g. g o o 5. sdmps {1.0 g. catechol {Toiling 59.7 0.31 24.0

It will be understood that modifications may be made in the preferred embodiment of the invention described herein without departing from the scope defined by the appended claims.

What we claim as new and desire to protect by Letters Patent of the United States is:

1. In a froth flotation process for the concentration of a niobium mineral selected from the group consisting of pyrochlore and niocalite .in which an aqueous dispersion of solids which contain at least one of said minerals is subjected to agitation and aeration in the presence of a frothing agent and a collector to produce a float product, the improvement which comprises adding catechol to said aqueous dispersion, continuing agitation and aeration of the aqueous dispersion, and separating and recovering niobium mineral concentrate as the float product.

2. The process according to claim 1 in which the float product which contains the niobium minerals is cleaned by subjecting it to at least one additional flotation step.

3. The process according to claim 1 in which the catechol is added to the aqueous dispersion as an aqueous solution.

4. The process according to claim 1 in which the catechol is agitated in an aqueous solution and aerated before being added to the aqueous dispersion.

5. The process according to claim 1 in which the catechol is added to the aqueous dispersion in the ratio of from about 0.5 to about 5 pounds of catechol per ton of solids.

6. In a two-stage froth flotation process for the recovery of a niobium mineral selected from the group consisting of pyrochlore and niocalite from an aqueous dispersion of solids which contain at least one of said minerals, the improvement which comprises providing in the aqueous dispersion an amine collecting agent and a frothing agent; subjecting said dispersion to agitation and aeration in a first-stage flotation step at a pH above about 10; removing the resultant first-stage float product, reducing the pH value of the residual dispersion after separation of the first-stage float product to a pH value below about 10, adding catechol to said residual dispersion, subjecting said residual dispersion, in the presence of a frothing agent and a collecting agent, to agitation and aeration in a second flotation stage, and recovering niobium mineral in the float product of said second flotation stage.

7. The process according to claim 6 in which the pH value of the aqueous dispersion treated in the first-stage flotation step is within the range of from about 10 to about 13, and the pH value of the residual dispersion treated in the second flotation stage is within the range of from about 2 to about 10.

8. The process according to claim 6 in which catechol is added to the residual dispersion from the first stage flotation step in amount within the range of from about 0.5 to about 5 pounds per ton of solids fed to the firststage flotation step.

9. The process according to claim 6 in which the second flotation stage includes at least one secondary flotation step whereby the float product which contains the niobium mineral is cleaned.

10. The process according to claim 6 in which the catechol is added as an aqueous solution to the residual dispersion after separation of the float product from the first-stage flotation step.

11. The process according to claim 6 in which the pH value of the dispersion is reduced by addition to the firststage residual pulp of at least one member of the group consisting of sulphuric acid, hydrochloric acid, nitric acid, hydrofluosilicic acid and magnesium fluosilicate.

References Cited in the file of this patent UNITED STATES PATENTS 2,875,896 Last et a1. Mar. 3, 1959 

1. IN A FROTH FLOTATION PROCESS FOR THE CONCENTRATION OF A NIOBIUM MINERAL SELECTED FROM THE GROUP CONSISTING OF PYROCHLORE AND NIOCALITE IN WHICH AN AQUEOUS DISPERSION OF SOLIDS WHICH CONTAIN AT LEAST ONE OF SAID MINERALS IS SUBJECTED TO AGITATION AND AERATION IN THE PRESENCE OF A FROTHING AGENT AND A COLLECTOR TO PRODUCE A FLOAT PRODUCT, THE IMPROVEMENT WHICH COMPRISES ADDING CATECHOL TO SAID AQUEOUS DISPERSION, CONTINUING AGITATION AND AERATION OF THE AQUEOUS DISPERSION, AND SEPARATING AND RECOVERING NIOBIUM MINERAL CONCENTRATE AS THE FLOAT PRODUCT. 